Wireless receiving apparatus



Oct. 18, 1932. J. L. CALLAHAN 1,882,772

WIRELESS RECEIVING APPARATUS Filed March l, 1928 INVENTOR JOHN L. LLAHAN BIE/id,

A RNEY Patented Oct. 18, 1932 UNI-TED. STATE-s PATENT OFFICE, i I

JOHN L. CALLAHAN, 0F NEW YORK, N. Y., .ASSIGN'OR TO RADIO CORPORATION 0F AMERICA., A .CORPORATION 01E'VV DELAWARE wInELEss VmicnIvIne APPARATUS Application lmea mmh 1', 192s. serial No. 25s,1ss.-

This invention relates to a` method of and apparatus for receivinghigh frequency oscillations such as are used in radio transmission and `in particular to a method and apparatus for receiving continuous wave oscillations. f y

It is well known that transmission by continuous wave is preferable in some instances to transmission by dampedl waves for the reason that greater'distance can be covered bythe use of the same amount of power at the transmitting station.v rI he frequencies of the propagated 'waves in general use, however are too high to operate the diaphragm of a telephonev to produce a note audible to the human ear.k Means must accordingly be provided'to change or alter the frequency of the incoming signals to such a value that they produce in the telephones of the receiver a note which will be audible to the human ear. l

There are many known methods ofi alter-y ing or reducing the incoming frequency to such a value that it will operate a telephone diaphragm to set up audible note. One of thecommon methods of receptionnow in use utilizes the so-called su erheterodyne prinn ciple. The superhetero yne methodnow in general use has several disadvantages, the main one of which is that the low frequency high power oscillator-whichisconnected in after the long wave or intermediate frequency amplifier and generates oscillations which are combined with the oscillations in the intermediate frequency amplifier to produce a beat note at audible frequency sets up har monies which interfere with the incoming signal oscillations. That is, the harmonics of the low frequency high power oscillator beat with the high frequency oscillator to produce an intermediate frequency similar to that produced between the signal oscillations and they high frequency oscillator.

In my novel method and apparatus for receiving signals by continuous wave oscillations, I have overcome many of the disadvantages attendant on the use of receivers known heretofore.

According to my novel method I utilize a low power oscillator and also a high frequen- Another advantage to cy high power oscillator both'of which are connected in between the aerial inductance and the first detector which is generally followfed by a long wave amplifier, seconddetector and a low frequencyamplifier. Y

Although for the purpose of distinguishing the oscillators I have throughout the specification designated one oscillator asl the low power oscillator and the other as the high -power oscillator the'terms are'relative and are not intended to limit the scope of the invention.

fl he low power oscillator generates oscillatlons at a frequency differing-from the frequency ofthe high power oscillator by` anv intermediate frequency. The incoming signal oscillations beat with the high frequency high rpowered oscillator to produce a second `beat note at a'frequency which should differ `resultant beat note at audible frequency which is amplified and set up in the receiver.

An apparent outstanding advantage of a device arranged in accordance lwith my invention is that the added high frequency oscillator may be so weak that it .doesnot need shielding. This oscillator may infact be 'of a strength equivalent to the strength of `the incoming signal oscillations.

' A further advantage to'be gained by the that the high frequency low'fpower oscillator can operate at a frequency which differs from the frequency of the high power oscillator by a constant value and accordingly the oscillators may be mechanicallycoupled to tune as a single unit. VObviously since the antenna .inductance is tuned the use of my arrangement does not increase the number of tuning points over the number used inthe ordinary receiver of this type. c be gained by ,my invention lies in the fact that it can be adapted to broadcast receivers now in use sincey little utilization of my invention lies inthe factor no difficulty is encountered in breakingmoo into such receivers to couple in the high frequency low power oscillator.

Other objects and advantages will become apparent in part from the following specification and in part from the specification when read in connection with the accompanying drawing in which: Y

Fig. l illustrates diagrammatically my novel method and arrangement for receiving i o 'continuous waves.

" erates oscillations at a frequency which differs ,by a constant from the frequency of the oscillations generated by the high power oscillator 5. 5 is the high power highfrequency :oscillator which generates oscillations to beat with the oscillations of the incoming signal and' also with the oscillations of the low power high frequency oscillator. The relative positions of these two oscillators Vis immaterial, that is, oscillator 5 may be placed im after the weak oscillator l as shown in the .drawing or it may be placed ahead of the weakoscillator 4. 6 is the long wave ampli- Y fier which includes asfirst detector, an amplifier stage or stages and a second detector.

I The amplifier stages in this unit should con- -sist of two circuits each tuned to a different frequency or as indicated in the drawing consist of one unit which is tuned broad enough to passa band of frequencies, that is, oscilla- 40 tions at two frequencies which differ from each other by an audible frequency as indicated in the drawing. The oscillations in vthe intermediate frequency amplifier beat tol produce a resultance or beat note at an audible lfrequency which by means of the second detector sets up an audible note in the low fre- ;quency amplifier 7, which will be heard in the receiver 8.

i It will be understood that this method of reception may be carried out with broadcast receivers now in use by adding the low power oscillator.

Although for purposes of illustration I have fully described the at present preferred form of my inventionV and the operation thereof, I do not limit myself thereby except as marked out in the following claims:

l; The method of receiving radio signals .which consist in setting up oscillations at the signal frequency in a circuit, generating in said circuit a first local Voscillation of an amplitude similar to the amplitude of theoscillations at signal frequency, generating in said circuit additional local oscillations of an amplitude greater than the amplitude of said first named oscillations, and utilizing the components of said oscillations to operate 'an indicating device. v

2. A radio receiving system comprising an oscillation circuit responsive to signal frequencies, a. pair of high frequency oscillation generators including oscillation circuits associated with said first named circuit, one of said generators being of low power relative to the power of the other of said generators, means lfor tuning one of said generators to a frequency differing from said signal frequency by an intermediate frequency, means for tuning ,the other of said generators to a frequency differing from the frequency of said first named generator by a constant intermediate frequency, and a single control for both of said tuning means.

JOHN L. CALLAHAN.

While the frequencies ofthe oscillators and gg the intermediate amplifiers used areimmaterial, f or purposes of illustration 'assume the incoming signal as being at 500 kilocycles, `the weak oscillation as beingtuned to 501 kilocycles, the `high frequency high power .5 oscillator being tuned at 560 kilocycles and .thelong wave amplifier asl being tuned to 59 Y `and 60 kilocycles. A resultant 59 kilocycle Y beat note is obtained Vin the output circuit of the .first detector of the intermediate fre- 60 quency amplifier 6 from the beat note of the wealroscillator and the high power oscillator. TA 60 kilocycle note is obtained in the output ofthe first detector of the intermediate frequency amplifier from the incoming'signals at 500 kilocycles and the high power oscilf 

